System and method for reducing blind decoding for carrier aggregation

ABSTRACT

A method for processing a control channel at a user agent (UA) to identify at least one of an uplink and a downlink resource grant within a wireless communication system wherein resource grants are received using control channel element (CCE) subsets wherein each CCE subset is a control channel candidate, wherein the UA is configured to decode up to M control channel candidates per time period for single carrier operation, the method comprising the steps of, at the user agent, identifying N control channel candidates that are distributed among C carriers wherein N is less than M×C, attempting to decode each of the N identified control channel candidates to identify at least one of an uplink and a downlink resource grant and where a control channel candidate is successfully decoded, using the one of the uplink grant and the downlink grant to facilitate communication.

The present application claims priority to U.S. provisional patentapplication No. 61/183,444 which was filed on Jun. 2, 2009 and which istitled “System And Method For Reducing Blind Decoding For CarrierAggregation” and also claims priority to U.S. provisional patentapplication No. 61/293,276 which was filed on Jan. 8, 2010 and which istitled “System And Method For Reducing Blind Decoding For CarrierAggregation”

BACKGROUND

The present invention relates generally to data transmission in mobilecommunication systems and more specifically to methods for reducingblind decoding for carrier aggregation.

As used herein, the terms “user agent” and “UA” can refer to wirelessdevices such as mobile telephones, personal digital assistants, handheldor laptop computers, and similar devices or other User Equipment (“UE”)that have telecommunications capabilities. In some embodiments, a UA mayrefer to a mobile, wireless device. The term “UA” may also refer todevices that have similar capabilities but that are not generallytransportable, such as desktop computers, set-top boxes, or networknodes.

In traditional wireless telecommunications systems, transmissionequipment in a base station transmits signals throughout a geographicalregion known as a cell. As technology has evolved, more advancedequipment has been introduced that can provide services that were notpossible previously. This advanced equipment might include, for example,an evolved universal terrestrial radio access network (E-UTRAN) node B(eNB) rather than a base station or other systems and devices that aremore highly evolved than the equivalent equipment in a traditionalwireless telecommunications system. Such advanced or next generationequipment may be referred to herein as long-term evolution (LTE)equipment, and a packet-based network that uses such equipment can bereferred to as an evolved packet system (EPS). Additional improvementsto LTE systems/equipment will eventually result in an LTE advanced(LTE-A) system. As used herein, the term “access device” will refer toany component, such as a traditional base station or an LTE or LTE-Aaccess device (including eNBs), that can provide a UA with access toother components in a telecommunications system.

In mobile communication systems such as the E-UTRAN, an access deviceprovides radio access to one or more UAs. The access device comprises apacket scheduler for dynamically scheduling downlink traffic data packettransmissions and allocating uplink traffic data packet transmissionresources among all the UAs communicating with the access device. Thefunctions of the scheduler include, among others, dividing the availableair interface capacity between UAs, deciding the transport channel to beused for each UA's packet data transmissions, and monitoring packetallocation and system load. The scheduler dynamically allocatesresources for Physical Downlink Shared CHannel (PDSCH) and PhysicalUplink Shared CHannel (PUSCH) data transmissions, and sends schedulinginformation to the UAs through a scheduling channel.

Several different data control information (DCI) message formats areused to communicate resource assignments to UAs including, among others,a DCI format 0 for specifying uplink resources, DCI formats 1, 1A, 1B,1C, 1D, 2 and 2A for specifying downlink resources, and DCI formats 3and 3A for specifying power control information. Uplink specifying DCIformat 0 includes several DCI fields, each of which includes informationfor specifying a different aspect of allocated uplink resources.Exemplary DCI format 0 DCI fields include a transmit power control (TPC)field, a cyclic shift demodulation reference signal (DM-RS) field, amodulating coding scheme (MCS) and redundancy version field, a New DataIndicator (NDI) field, a resource block assignment field and a hoppingflag field. The downlink specifying DCI formats 1, 1A, 2 and 2A eachinclude several DCI fields that include information for specifyingdifferent aspects of allocated downlink resources. Exemplary DCI format1, 1A, 2 and 2A DCI fields include a HARQ process number field, an MCSfield, a New Data Indicator (NDI) field, a resource block assignmentfield and a redundancy version field. Each of the DCI formats 0, 1, 2,1A and 2A includes additional fields for specifying allocated resources.Other downlink formats 1B, 1C and 1D include similar information. Theaccess device selects one of the downlink DCI formats for allocatingresources to a UA as a function of several factors including UA andaccess device capabilities, the amount of data a UA has to transmit, theamount of communication traffic within a cell, etc.

LTE transmissions are divided into eight separate 1 millisecondsub-frames. DCI messages are synchronized with sub-frames so that theycan be associated therewith implicitly as opposed to explicitly, whichreduces control overhead requirements. For instance, in LTE frequencydivision duplex (FDD) systems, a DCI message is associated with anuplink sub-frame four milliseconds later so that, for example, when aDCI message is received at a first time, the UA is programmed to use theresource grant indicated therein to transmit a data packet in thesub-frame four milliseconds after the first time. Similarly, a DCImessage is associated with a simultaneously transmitted downlinksub-frame. For example, when a DCI message is received at a first time,the UA is programmed to use the resource grant indicated therein todecode a data packet in a simultaneously received traffic datasub-frame.

During operation, LTE networks use a shared Physical Downlink ControlCHannel (PDCCH) to distribute assignment messages including DCI messagesamongst UAs. The DCI messages for each UA as well as other sharedcontrol information are separately encoded. The PDCCH includes aplurality of control channel elements (CCEs) that are used to transmitDCI messages from an access device to UAs. An access device selects oneor an aggregation of CCEs to be used to transmit a DCI message to a UA,the CCE subset selected to transmit a message depending at least in parton perceived communication conditions between the access device and theUA. For instance, where a high quality communication link is known toexist between an access device and a UA, the access device may transmitdata to the UA via a single one of the CCEs and, where the link is lowquality, the access device may transmit data to the UA via a subset oftwo, four or even eight CCEs, where the additional CCEs facilitate amore robust transmission of an associated DCI message. The access devicemay select CCE subsets for DCI message transmission based on many othercriteria.

Because a UA does not know exactly which CCE subset or subsets are usedby an access device to transmit DCI messages to the UA, in existing LTEnetworks, the UA is programmed to attempt to decode many different CCEsubset candidates when searching for a DCI message. For instance, a UAmay be programmed to search a plurality of single CCEs for DCI messagesand a plurality of two CCE subsets, four CCE subsets and eight CCEsubsets to locate a DCI message. To reduce the possible CCE subsets thatneed to be searched, access devices and UAs have been programmed so thateach access device only uses specific CCE subsets to transmit DCImessages to a specific UA corresponding to a specific data trafficsub-frame and so that the UA knows which CCE subsets to search. Forinstance, in current LTE networks, for each data traffic sub-frame, a UAsearches six single CCEs, six 2-CCE subsets, two 4-CCE subsets and two8-CCE subsets for DCI messages for a total of sixteen CCE subsets. Thesixteen CCE subsets are a function of a specific Radio Network TemporaryIdentifier (RNTI) assigned to a UA 10 and vary from one sub-frame to thenext. This search space that is specific to a given UA is referred tohereinafter as “UA specific search space”.

Where an access device may transmit DCI messages in two or more DCIformat sizes, a separate decoding attempt for each CCE subset candidatefor each possible DCI format size is required. For instance, where twoDCI format sizes are used, each of the 16 CCE subset candidatesdescribed above would have to be searched twice for a total of 32searches or decoding attempts.

In addition to searching the UA specific search space, each UA alsosearches a common search space for each sub-frame. The common searchspace includes CCE subsets that do not change from sub-frame tosub-frame and that, as the label implies, are common to all UAs linkedto an access device. For instance, in current LTE networks the commonsearch space includes four 4-CCE subsets and two 8-CCE subsets for atotal of six CCE subsets in the common search space. Here, as in thecase of the UA specific search space, where there are two DCI formatsizes, each of the six CCE subset in the common space is searched twice,once for each format size, and the total number of searches is twelve.

Hereinafter, unless indicated otherwise, CCE subsets that include oneCCE will be referred to as “Aggregation level 1” subsets. Similarly,subsets that include two CCEs will be referred to as “Aggregation level2” subsets, subsets that include four CCEs will be referred to as“Aggregation level 4” subsets, and subsets that include eight CCEs willbe referred to as “Aggregation level 8” subsets.

Thus, in current LTE networks, a UE must perform a potential maximum of44 blind decodes per traffic data sub-frame (e.g., 32 UA specific searchspace blind decodes and 12 common search space blind decodes) for eachdistinct RNTI value that is used to define a user-specific search space.(Currently for LTE, only one RNTI value per UA is used to define theuser-specific search space for a given sub-frame.)

In many cases it is desirable for an access device to transmit a largeamount of data to a UA or for a UA to transmit large amounts of data toan access device in a short amount of time. For instance, a series ofpictures may have to be transmitted to an access device over a shortamount of time. As another instance, a UA may run several applicationsthat all have to receive data packets from an access device essentiallysimultaneously so that the combined data transfer is extremely large.One way to increase the rate of data transmission is to use multiplecarriers (i.e., multiple frequencies) to communicate between an accessdevice and UAs. For example, a system may support five differentcarriers (i.e. frequencies) and eight sub-frames so that five separateeight sub-frame uplink and five separate eight sub-frame downlinktransmission streams can be generated in parallel. Communication viamultiple carriers is referred to as carrier aggregation.

In the case of carrier aggregation, DCI message searching must beperformed for each carrier employed. Thus, for instance, if a systemuses five LTE carriers (with each carrier following the current LTEdesign), a UE must perform a potential maximum of 44 blind decodes pertraffic data sub-frame per carrier for a total of 220 blind decodes.Thus, where large numbers (e.g., 220 per sub-frame) of blind decodes arerequired, battery charge can be depleted rapidly and processingrequirements become excessive.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this disclosure, reference is nowmade to the following brief description, taken in connection with theaccompanying drawings and detailed description, wherein like referencenumerals represent like parts.

FIG. 1 is a schematic diagram showing components of a communicationsystem including a user agent (UA) for implementing reduced blinddecoding for carrier aggregation;

FIG. 2 is an illustration of carrier aggregation in a communicationsnetwork where each component carrier has a bandwidth of 20 MHz and thetotal system bandwidth is 100 MHz;

FIG. 3 is an illustration of aggregation levels and search spaces thatmay be present within the PDCCH;

FIG. 4 is a table showing aggregation levels for different UA-specificand common search spaces;

FIGS. 5 a-5 e illustrate various field formats for signaling aggregationlevels to be searched by a UA;

FIG. 6 is a flow chart illustrating one method for indicating ifadditional carriers should be searched via a DCI message;

FIG. 7 is a table showing exemplary configuration aggregation levels forthe anchor carrier and remaining active carriers;

FIG. 8 is a table showing a number of PDCCH candidates to decode forboth an anchor carrier and remaining active carriers;

FIG. 9 illustrates a MAC control element for signaling which aggregationlevels a UA should monitor on multi-carrier PDCCHs;

FIG. 10 is a table showing target aggregation levels of an anchorcarrier and the resulting aggregation levels that are monitored by theUA of FIG. 1;

FIG. 11 is a table showing target aggregation levels of an anchorcarrier and the resulting aggregation levels that are monitored by theUA of FIG. 1;

FIG. 12 is a table showing detected aggregation levels of an anchorcarrier and the resulting aggregation levels to search on non-anchorcarriers;

FIG. 13 is a table showing an example mapping of channel qualityinformation (CQI) values to corresponding aggregation levels;

FIG. 14 is an illustration showing common and UA-specific search spacesfor anchor carriers and other active carriers;

FIG. 15 is a table illustrating exemplary search space aggregationlevels, CCE subset sizes and the number of PDCCH candidates;

FIG. 16 is a diagram of a wireless communications system including a UAoperable for some of the various embodiments of the disclosure;

FIG. 17 is a block diagram of a UA operable for some of the variousembodiments of the disclosure;

FIG. 18 is a diagram of a software environment that may be implementedon a UA operable for some of the various embodiments of the disclosure;

FIG. 19 is an illustrative general purpose computer system suitable forsome of the various embodiments of the disclosure; and

FIG. 20 is a diagram of a primary and secondary search space.

DETAILED DESCRIPTION

It has been recognized that the amount of blind decoding may beminimized in multi-carrier communication network systems.

To this end, some embodiments include a method for processing a controlchannel at a user agent (UA) to identify at least one of an uplink and adownlink resource grant within a wireless communication system whereinresource grants are received using control channel element (CCE) subsetswherein each CCE subset is a control channel candidate, wherein the UAis configured to decode up to M control channel candidates per timeperiod for single carrier operation, the method comprising the steps of,at the user agent, identifying N control channel candidates that aredistributed among C carriers wherein N is less than M×C, attempting todecode each of the N identified control channel candidates to identifyat least one of an uplink and a downlink resource grant and where acontrol channel candidate is successfully decoded, using the one of theuplink grant and the downlink grant to facilitate communication.

In some cases the step of identifying N control channel candidatesincludes identifying candidates that are evenly distributed among the Ccarriers.

In some cases the step of identifying N control channel candidatesincludes identifying candidates that are unevenly distributed among theC carriers.

In some cases one of the carriers is designated as an anchor carrier andother carriers are non-anchor active carriers and wherein the step ofidentifying includes, for the anchor carrier, identifying a total of Pcontrol channel candidates and, for all the non-anchor active carriers,identifying a total of R control channel candidates, where the R controlchannel candidates are distributed among the non-anchor active carriersand wherein the sum of P and R is equal to N.

In some cases the R candidates are evenly distributed among thenon-anchor active carriers. In some cases the N control channelcandidates are evenly distributed among all of the carriers. In somecases the total number P of control channel candidates identified forthe anchor carrier is M. In some cases the step of identifying includesidentifying a different set of control channel candidates for each ofthe carriers.

In some cases control channel candidates include at least firstaggregation level and second aggregation level candidates, each firstaggregation level candidate including a first number of the CCEs andeach second aggregation level candidate including a second number ofCCEs that is different than the first number of CCEs and wherein thestep of identifying includes identifying specific control channels foreach aggregation level and each active carrier. In some cases N isgreater than M. In some cases the step of identifying N control channelsincludes dynamically identifying the N control channel candidates.

In some cases the step of dynamically identifying includes receivingdata from an access device indicating control channel candidates. Insome cases the step of receiving data from an access device includesreceiving one of a DCI formatted message, a MAC formatted message and anRRC formatted message. In some cases the step of identifying includesidentifying no more than M control channel candidates to be decoded foreach of the carriers. In some cases one of the carriers is an anchorcarrier and the other carriers are non-anchor active carriers andwherein the step of identifying includes identifying less than Mcandidates for each non-anchor active carrier.

Other embodiments include an apparatus for processing a control channelat a user agent (UA) to identify at least one of an uplink and adownlink resource grant within a wireless communication system whereinresource grants are received using control channel element (CCE) subsetswherein each CCE subset is a control channel candidate, wherein the UAis configured to decode up to M control channel candidates per timeperiod for single carrier operation, the apparatus comprising aprocessor programmed to perform the steps of, identifying N controlchannel candidates that are distributed among C carriers wherein N isless than M×C, attempting to decode each of the N identified controlchannel candidates to identify at least one of an uplink and a downlinkresource grant and where a control channel candidate is successfullydecoded, using the one of the uplink grant and the downlink grant tofacilitate communication.

In some cases the processor is programmed to perform the step ofidentifying N control channel candidates by identifying candidates thatare evenly distributed among the C carriers. In some cases the processoris programmed to perform the step of identifying N control channelcandidates by identifying candidates that are unevenly distributed amongthe C carriers.

In some cases one of the carriers is designated as an anchor carrier andother carriers are non-anchor active carriers and wherein the processoris programmed to perform the step of identifying by, for the anchorcarrier, identifying a total of P control channel candidates and, forall the non-anchor active carriers, identifying a total of R controlchannel candidates, where the R control channel candidates aredistributed among the active carriers and wherein the sum of P and R isequal to N. In some cases the R candidates are evenly distributed amongthe non-anchor active carriers. In some cases the total number P ofcontrol channel candidates identified for the anchor carrier is M. Insome cases the processor is programmed to perform the step ofidentifying by receiving data from an access device indicating controlchannel candidates for the carriers. In some cases the step of receivingdata from an access device includes receiving one of a DCI formattedmessage, a MAC formatted message and an RRC formatted message.

Still other embodiments include a method for processing a controlchannel at an access device to transmit at least one of an uplink and adownlink resource grant within a wireless communication system to a useragent wherein resource grants are specified by control channel element(CCE) subsets wherein each CCE subset is a control channel candidate,wherein a UA is configured to decode up to M control channel candidatesper time period for single carrier operation to identify a resourcegrant, the method comprising the steps of, at the access device, (i)identifying N control channel candidates to be associated with the Ccarriers wherein N is less than M×C, (ii) selecting at least one of theN control channel candidate subset candidates to code at least one of anuplink grant and a downlink grant for at least one of the C carriers tobe used by a UA, (iii) using the selected control channel candidate tocode the at least one an uplink grant and a downlink grant and (iv)transmitting the grant to the UA via the selected control channelcandidate.

In some cases the step of selecting includes selecting at least one ofthe N control channel candidates for each of the C carriers, the step ofusing includes using the selected control channel candidates to code atleast one of an uplink and a downlink grant for each of the C carriersand the step of transmitting includes transmitting the grants to the UAvia the selected control channel candidates. In some cases the N controlchannel candidates include N/C candidates on each of the C carriers. Insome cases the step of selecting at least one control channel candidatefor a carrier includes selecting a control channel candidate on thecarrier.

To the accomplishment of the foregoing and related ends, the invention,then, comprises the features hereinafter fully described. The followingdescription and the annexed drawings set forth in detail certainillustrative aspects of the invention. However, these aspects areindicative of but a few of the various ways in which the principles ofthe invention can be employed. Other aspects, advantages and novelfeatures of the invention will become apparent from the followingdetailed description of the invention when considered in conjunctionwith the drawings.

The various aspects of the subject invention are now described withreference to the annexed drawings, wherein like numerals refer to likeor corresponding elements throughout. It should be understood, however,that the drawings and detailed description relating thereto are notintended to limit the claimed subject matter to the particular formdisclosed. Rather, the intention is to cover all modifications,equivalents, and alternatives falling within the spirit and scope of theclaimed subject matter.

As used herein, the terms “component,” “system” and the like areintended to refer to a computer-related entity, either hardware, acombination of hardware and software, software, or software inexecution. For example, a component may be, but is not limited to being,a process running on a processor, a processor, an object, an executable,a thread of execution, a program, and/or a computer. By way ofillustration, both an application running on a computer and the computercan be a component. One or more components may reside within a processand/or thread of execution and a component may be localized on onecomputer and/or distributed between two or more computers.

The word “exemplary” is used herein to mean serving as an example,instance, or illustration. Any aspect or design described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other aspects or designs.

Furthermore, the disclosed subject matter may be implemented as asystem, method, apparatus, or article of manufacture using standardprogramming and/or engineering techniques to produce software, firmware,hardware, or any combination thereof to control a computer or processorbased device to implement aspects detailed herein. The term “article ofmanufacture” (or alternatively, “computer program product”) as usedherein is intended to encompass a computer program accessible from anycomputer-readable device, carrier, or media. For example, computerreadable media can include but are not limited to magnetic storagedevices (e.g., hard disk, floppy disk, magnetic strips . . . ), opticaldisks (e.g., compact disk (CD), digital versatile disk (DVD) . . . ),smart cards, and flash memory devices (e.g., card, stick). Additionallyit should be appreciated that a carrier wave can be employed to carrycomputer-readable electronic data such as those used in transmitting andreceiving electronic mail or in accessing a network such as the Internetor a local area network (LAN). Of course, those skilled in the art willrecognize many modifications may be made to this configuration withoutdeparting from the scope or spirit of the claimed subject matter.

In general, the inventive system and methods have been developed toreduce the number of control channel element subsets that need to besearched for DCI messages as a function of communication systemoperating parameters which in turn reduces battery power required tofacilitate DCI searching as well as reducing processing time dedicatedto DCI searching. To this end, for instance, where a current standardspecifies that the number of CCE subset searches (M) to be performed oneach carrier for each sub-frame is 22, based on communication systemoperating parameters, the number for a given carrier may be reduced toN, a number less than 22, in any of several different ways which aredescribed hereafter. This process of reducing the number of CCE subsetsto be searched is performed dynamically as system operating parameterschange in at least some embodiments. After N CCE subsets have beenselected for a given carrier, the N subsets are blindly decoded toidentify DCI formatted messages.

Referring now to the drawings wherein like reference numerals correspondto similar elements throughout the several views, FIG. 1 is a schematicdiagram illustrating an exemplary multi-channel communication system 30including a user agent (UA) 10 and an access device 12. UA 10 includes,among other components, a processor 14 that runs one or more softwareprograms wherein at least one of the programs communicates with accessdevice 12 to receive data from, and to provide data to, access device12. When data is transmitted from UA 10 to device 12, the data isreferred to as uplink data and when data is transmitted from accessdevice 12 to UA 10, the data is referred to as downlink data. Accessdevice 12, in one implementation, may include an E-UTRAN node B (eNB) orother network component for communicating with UA 10.

To facilitate communications, a plurality of different communicationchannels are established between access device 12 and UA 10. For thepurposes of the present disclosure, referring to FIG. 1, the importantchannels between access device 12 and UA 10 include a Physical DownlinkControl CHannel (PDCCH) 70, a Physical Downlink Shared CHannel (PDSCH)72 and a Physical Uplink Shared CHannel (PUSCH) 74. As the labelimplies, the PDCCH is a channel that allows access device 12 to controlUA 10 during downlink data communications. To this end, the PDCCH isused to transmit scheduling or control data packets referred to asdownlink control information (DCI) packets to the UA 10 to indicatescheduling to be used by UA 10 to receive downlink communication trafficpackets or transmit uplink communication traffic packets or specificinstructions to the UA (e.g. power control commands, an order to performa random access procedure, a semi-persistent scheduling activation ordeactivation). A separate DCI packet may be transmitted by access device12 to UA 10 for each traffic packet/sub-frame transmission.

Exemplary DCI formats include format 0 for specifying uplink resourcesand DCI formats 1, 1A, 1B, 1C, 1D, 2 and 2A for specifying downlinkresources. Other DCI formats are contemplated. Exemplary DCI packets areindicated by communication 71 on PDCCH 70 in FIG. 1.

Referring still to FIG. 1, exemplary traffic data packets or sub-frameson PDSCH 72 are labeled 73. In at least some embodiments a trafficpacket will be transmitted via the same carrier (i.e., the samefrequency) as an associated DCI packet. The PUSCH 74 is used by UA 10 totransmit data sub-frames or packets to access device 12. Exemplarytraffic packets on PUSCH 74 are labeled 77.

Carrier aggregation is used to support wider transmission bandwidths andincrease the potential peak data rate for communications between UA 10,access device 12 and/or other network components. In carrieraggregation, multiple component carriers are aggregated and may beallocated in a sub-frame to a UA 10 as shown in FIG. 2. FIG. 2 showscarrier aggregation in a communications network where each componentcarrier has a bandwidth of 20 MHz and the total system bandwidth is 100MHz. As illustrated, the available bandwidth 100 is split into aplurality of carriers 102. UA 10 may receive or transmit on multiplecomponent carriers (up to a total of five carriers 102 in the exampleshown in FIG. 2), depending on the UA's capabilities. In some cases,depending on the network deployment, carrier aggregation may occur withcarriers 102 located in the same band and/or carriers 102 located indifferent bands. For example, one carrier 102 may be located at 2 GHzand a second aggregated carrier 102 may be located at 800 MHz.

Referring to FIG. 3, an exemplary PDCCH includes a plurality of controlchannel elements (CCEs) 110 that are used to transmit DCI formattedmessages from access device 12 to UA 10. In the illustrated example thePDCCH includes thirty-eight CCEs. In other embodiments other numbers ofCCEs may be employed. Access device 12 selects one or an aggregation ofCCEs to be used to transmit a DCI message to UA 10, the CCE subsetselected to transmit a message depending at least in part on perceivedcommunication conditions between the access device and the UA. Forinstance, where a high quality communication link is known to existbetween an access device and a UA, the access device may transmit datato the UA via a single one of the CCEs (see 116) and, where the link islow quality, the access device may transmit data to the UA via a subsetof two (see 118), four (see 120) or even eight CCEs (see 122), where theadditional CCEs facilitate a more robust transmission of an associatedDCI message. The access device may select CCE subsets for DCI messagetransmission based on many other criteria.

In current LTE networks, because UA 10 does not know exactly which CCEsubset or subsets (e.g., 116, 118, 120, 122, etc.) are used by an accessdevice to transmit DCI messages to UA 10, UA 10 is programmed to attemptto decode many different CCE subset candidates when searching for a DCImessage. For instance, UA 10 may be programmed to search a plurality ofsingle CCEs for DCI messages and a plurality of two CCE subsets, fourCCE subsets and eight CCE subsets to locate a DCI message.

To reduce the possible CCE subsets that need to be searched by a UA 10,access devices and UAs have been programmed so that each access deviceonly uses specific CCE subsets to transmit DCI messages to a specific UA10 corresponding to a specific data traffic sub-frame and so that the UAknows which CCE subsets to search. For instance, as shown in FIG. 3, incurrent LTE networks, for each data traffic sub-frame, a standardrequires a UA to search six single CCEs (see exemplary clear single CCEs116), six 2-CCE subsets (see exemplary six clear subsets 118), two 4-CCEsubsets (see exemplary two clear subsets 120) and two 8-CCE subsets (seeexemplary two clear subsets 120) for DCI messages for a total of sixteenCCE subsets. The sixteen CCE subsets vary pseudo-randomly for differentsub-frames as a function of a UA's assigned RNTI value. This searchspace that is specific to a given UA is referred to hereinafter as “UAspecific search space” 114.

Referring still to FIG. 3, in addition to searching UA specific searchspace 114, UA 10 also searches a “common search space” 112 for eachsub-frame. Common search space 112 includes CCE subsets that do notchange from sub-frame to sub-frame and that, as the label implies, arecommon to all UAs communicating with an access device 12. For instance,in current LTE networks the common search space includes four 4-CCEsubsets (see exemplary four clear subsets 124) and two 8-CCE subsets(see exemplary two clear subsets 126) for a total of six CCE subsets incommon search space 112. In at least some implementations common searchspace 112 may begin at CCE 0 within the PDCCH and continue to CCE 15 asshown in FIG. 3.

Thus, in current LTE networks a total of twenty-two different CCEsubsets may be searched for each sub-frame. Where a system employs DCImessages in which the UE is configured to decode DCI messages that havetwo different lengths, a total of 44 different decoding attempts may berequired for each sub-frame, a separate decode attempt for each CCEsubset-DCI format length combination.

Hereinafter, unless indicated otherwise, CCE subsets that include oneCCE will be referred to as “Aggregation level 1” subsets. Similarly,subsets that include two CCEs will be referred to as “Aggregation level2” subsets, subsets that include four CCEs will be referred to as“Aggregation level 4” subsets, and subsets that include eight CCEs willbe referred to as “Aggregation level 8” subsets. A higher aggregationlevel indicates that the number of CCEs used to transmit a particularDCI is larger (e.g., aggregation level 8 is higher than aggregationlevel 4) and is therefore more robust assuming a given set of channelconditions. Accordingly, UA's 10 with poor channel conditions may beassigned higher aggregation levels to ensure the UAs 10 can successfullydecode DCI messages received on the PDCCH.

Referring now to FIG. 4, a table is provided that summarizes theinformation in FIG. 3 by showing aggregation levels for the UA-specificand common search spaces 114 and 112, respectively, and the number ofPDCCH (CCE subset) candidates to be searched by UA 10 at eachaggregation level. In UA-specific search space 114, at aggregationlevels 1 and 2, there are 6 PDCCH or CCE subset candidates each, and ataggregation levels 4 and 8, there are 2 PDCCH candidates each. In commonsearch space 112, at aggregation level 4 there are 4 PDCCH candidatesand at aggregation level 8 there are 2 PDCCH candidates.

For carrier aggregation, where separate coding is used for eachcarrier's PDCCH, the blind decoding requirements for UA 10 can becomeprohibitive. Blind decoding directly affects UA 10 battery life and UA10 processing requirements. Reducing the maximum possible number ofrequired blind decodes not only reduces the computational expense ofperforming blind decodes, but also reduces the amount of time requiredto perform the blind decodes.

The present disclosure describes several different ways to reduce theamount of UA blind decoding in multi-carrier communication networks.While each solution is described separately below, it should beappreciated that various aspects of the different solutions may becombined in at least some embodiments to result in other usefulsolutions. In at least some embodiments access device 12 determines anappropriate subset of CCE subsets to be monitored by each UA 10, encodesthe subset information and transmits the subset information to each UA10 so that each UA 10 decodes only a subset of available CCE subsets andaggregation levels within the PDCCH. Alternatively, each UA 10 mayindependently determine a subset of the CCE subset candidates to besearched/decoded. Here, UA 10 may rely upon information known to both UA10 and access device 12 to identify the subset. The information mayinclude the quality of the connection between access device 12 and UA10, previous traffic flow between UA 10 and access device 12, previousCCE subset search results on one or more carriers, or any otherinformation known to both access device 12 and UA 10.

Solution 1

Referring again to FIG. 1, in some embodiments, access device 12 isprogrammed to transmit a message to UA 10 indicating a reduced subset ofaggregation levels to be searched. As one alternative, this message maytake any of several different forms including a DCI message, a MACcontrol element, an RRC message, etc., where the message includes ainformation field which is used to determine the blind decoding rule,for example, “decode rule field”. Exemplary decode rule field formatsare illustrated in FIG. 5( a) through 5(e). In FIGS. 5( a)-5(e),elements identified by numeral 114 comprise varying aggregation levelsin UA-specific search space 114 (see again FIG. 3) that may be enabledfor searching and elements identified by numeral 112 comprise varyingaggregation levels in common search space 112 (see FIG. 3) that may beenabled for searching. Enabled aggregation levels are shown as clear anddisabled levels are shown in cross hatch.

With specific reference to FIG. 5( a), a four-bit field 128 is used tospecify the aggregation levels that are enabled (or disabled) for aparticular UA 10. In FIG. 5( a), the first bit in the field correspondsto aggregation level 1 in UA-specific search space 114, the second bitto aggregation level 2 in UA-specific search space 114, the third bit toaggregation level 4 in UA-specific search space 114 and common searchspace 112, and the fourth bit to aggregation level 8 in UA-specificsearch space 114 and common search space 112. In FIG. 5( a), bits 1, 2,and 4 are set to 1, while bit 3 is set to 0. As such, aggregation levels1, 2, and 8 are enabled, while aggregation level 4 is disabled.

In FIG. 5( b), six-bit field 130 extends the concept illustrated in FIG.5( a). In FIG. 5( b), six-bit field 130 allows aggregation levels inboth the UA-specific search spaces 114 and common search spaces 112 tobe individually enabled or disabled. The first four bits of six-bitfield 130 correspond to the four aggregation levels in the UA-specificsearch space 114, and the last two bits in the field correspond to thetwo aggregation levels in the common search space 112.

In FIG. 5( c), two-bit field 132 specifies one of the four possibleaggregation levels as the target aggregation level for which searchingshould be performed. In this example, only the specified aggregationlevel is searched by UA 10. In FIG. 5( c), two-bit field 132 is mappedto various aggregation levels in accordance with the following rules: atwo-bit field 132 value of ‘00’ indicates aggregation Level 1 inUA-specific search space 114, a value of ‘01’ indicates aggregationlevel 2 in UA-specific search space 114, a value of ‘10’ indicatesaggregation level 4 in UA-specific search space 114 and common searchspace 112, and a value of ‘11’ indicates aggregation level 8 inUA-specific search space 114 and common search space 112. In FIG. 5( d),two-bit field 134 specifies a target aggregation level. In this example,the target aggregation level and all higher aggregation levels aresearched. The same example field-to-aggregation-level mappings asdescribed for FIG. 5( c) may be implemented in the present example.

In FIG. 5( e), two-bit field 134 specifies a target aggregation level.In this example, however, the target aggregation level in addition tothe immediately adjacent aggregation levels are searched by UA 10 (i.e.,aggregation levels immediately above and below the target levelspecified by two-bit field 134). The same examplefield-to-aggregation-level mappings as for FIGS. 5( c) and 5(d) may beimplemented in the present example.

In each of the examples of FIGS. 5( a) through 5(e), the identifiedaggregation levels may apply to a single carrier or to multiplecarriers. In addition, the two-bit field formats of FIGS. 5( c) through5(e) may apply to the UA-specific search area, the common search area,or both. The exact configuration could be determined via pre-set rulesand/or higher layer signaling. This information field can be carried inthe PDCCH signaling, MAC Control elements or the RRC signaling. Inanother alternative, the “decode rule field” may be hard-coded in the UA10 which may reduce the signaling overhead.

Solution 2

In other embodiments UA 10 is assigned a set of active carriers and oneof the active carriers is assigned as an anchor carrier. Here, an activecarrier is a carrier for which UA 10 is buffering received symbols forpotential traffic and control reception. The CCE subsets of activecarriers are searched in a specific order, beginning with the anchorcarrier. Here, each DCI format is configured to contain an additionalsignaling bit in a “search continue field” to indicate whether searchingshould continue (e.g., signaling bit=‘1’, indicating there are more DCIsto be found) or whether searching should terminate (e.g., signalingbit=‘0’, indicating there are no more DCIs to be found). If a new DCIformat is defined, an extra signaling bit or search continue field maybe added to any new DCI formats. Alternatively, padding bits in existingDCI formats may be used to provide the additional signaling bit.Currently, any padding bits that are added to the current DCI formats tosatisfy certain length constraints (see section 5.3.3.1 of 36.212) havea value of 0. The padding bits (if present) may therefore be used assignaling bits. Finally, if no padding bits are available and the DCIformats remain unchanged, one of the existing bits may be redefined toindicate whether searching should continue. Example existing bits thatmay be reassigned to provide this functionality includes one of thePUCCH or PUSCH power control bits.

Referring to FIG. 6, an exemplary process 41 consistent with thissolution is illustrated. At block 43 CCEs are received on one ormultiple PDCCHs. At block 45, the CCE subsets are decoded on one carrierto obtain a DCI message. At block 47 the signaling bit in the searchcontinue field is identified. At block 49, where the signaling bit valueis “1”, control passes back up to block 45 where CCE subsets associatedwith the next carrier are searched for DCI messages. At block 49, whenthe signaling bit is “0”, searching stops at block 51 for the sub-frame.

In this implementation, if a missed detection occurs on one of thePDCCHs, UA 10 continues to search for further DCIs because UA 10considers the last signaling bit that it has seen to have a value of 1.A false detection may cause difficulties, but the probability of a falsedetection (false positive) is lower than that of a missed detection(false negative). Some additional search rules as described in thepresent disclosure (e.g., only aggregation levels greater than or equalto the aggregation level used on the anchor carrier are used) may beimplemented in combination with the search continue field.

Alternatively, one or more DCI messages may contain an indication of thetotal number of DCI messages for UA 10. Upon detection of such amessage, the UA 10 knows how many DCI messages are intended for it inthe current sub-frame. Upon detection of the indicated number of DCImessages, the UA 10 can stop searching. This allows UA 10 to know whento stop searching, regardless of the search algorithm and may allow someimplementation specific techniques for reducing blind decoding.Alternatively, one or more DCI messages may contain an index for thenext component carrier that UA 10 should search which may contain moreDCIs for the UA 10.

Solution 3

In some embodiments access device 12 may indicate to UAs 10 whether aparticular aggregation level is supported using higher layer (e.g., RRC)signaling for each UA 10 and, potentially, for each UA 10 on eachcarrier. Because multiple carriers may be allocated to UAs 10 havinggood channel conditions, smaller aggregation levels may be sufficient totransmit DCI messages.

FIG. 7 is a table showing exemplary configuration aggregation levels foran anchor carrier and remaining active carriers wherein levels to besearched are shown as clear and levels that are not to be searched areshown in cross hatch. In FIG. 7, UA 10 is configured to decode theaggregation level 1, 2, and 8 CCE subsets on the anchor carrier in theUA-specific search space and aggregation level 4 and 8 CCE subsets inthe common search space. UA 10 is also configured to decode theaggregation level 1 and 2 CCE subsets on the non-anchor carriers in theUA-specific search space and aggregation level 4 and 8 CCE subsets inthe common search space. The CCE subsets can be indicated to the UA forexample using the message illustrated in FIG. 5 b.

In other embodiments higher layer signaling may indicate the number ofCCE subset candidates to be searched for each aggregation level and eachcarrier. To this end, see FIG. 8 that shows a table indicating that a UA10 is configured to decode a full complement of CCE subsets for ananchor carrier and to decode a limited subset of the CCE subsetcandidates for the remaining active carriers. There are many types ofsignaling which could be used to support this configuration. In anotherembodiment, the number of CCE subset candidates to be searched for eachaggregation level and each carrier may be pre-set by the standards orhard-coded in the UA 10.

In some implementations, a total number of CCE subset candidates may beestablished for the non-anchor carriers where the total number of CCEsubset candidates are distributed (either evenly or unevenly) among thenon-anchor carriers. Alternatively, a total number of candidates isestablished for all carriers, which are distributed among all thecarriers (including, for example, anchor and non-anchor carriers). Forexample, a UA 10 may be configured to support decoding a maximum of 44CCE subsets regardless of the number of carriers currently being used.Upon determining the number of carriers to monitor, the UA distributesthe 44 decoding attempts among the carriers. For example, if the anchorcarrier is always allocated 22 CCE subsets as in FIG. 3, then there are22 CCE subsets available for the remaining active carriers. If the UA 10is currently monitoring 2 non-anchor carriers, then each carrier isallocated 11 CCE subsets, which are distributed among the supportedaggregation levels.

Solution 4

In some embodiments higher layer signaling at the RRC level specifyingwhich aggregation levels or CCE subsets a particular UA 10 shouldmonitor may be slow and incur significant overhead. Where a UA'stransmission channel is varying, for example, some dynamic tracking maybe required so that a UA 10 can be instructed to monitor smallaggregation levels (e.g., aggregation levels of 1 or 2) when the UA'stransmission channel is good and large aggregation levels (e.g.,aggregation levels of 4 or 8) when the UA's transmission channel ispoor. For a mobile UA 10, RRC signaling may be unable to quickly track achange in transmission channel quality. As such, contact with the UA 10may be lost if UA 10's transmission channel suddenly degrades fasterthan access device 12 is able to react.

An alternative to RRC signaling includes a new MAC control element thatallows access device 12 to signal changes in the aggregation levels thata UA 10 should search. Referring to FIG. 9, an exemplary MAC controlelement 59 is illustrated for signaling which aggregation levels a UA 10should monitor on multi-carrier PDCCHs. In FIG. 9, a value of 1 in thecorresponding bit position means that UA 10 should monitor thataggregation level in the anchor carrier's, or non-anchor carrier'sPDCCH, as appropriate, while a value of 0 means that UA 10 does not needto monitor the corresponding aggregation level. Accordingly, flags A1,A2, A4 and A8 in FIG. 9 indicate the aggregation level for the anchorcarrier, while flags C1, C2, C4 and C8 indicate the aggregation levelfor non-anchor carriers. The example MAC control element illustrated inFIG. 9 has a fixed payload length of one byte. For cases involvingnon-adjacent (in frequency) carriers, a four-bit field (C1, C2, C4, C8)may be provided for each of the distinct carriers used by UA 10. Theencoding of 69 and 71 can for example be as in FIG. 5 a.

The MAC control element of FIG. 9 is exemplary only. Other MAC controlelement variations may be implemented. For example, aggregation levelflags may be provided separately for the common and UA-specific searchareas (e.g., a total of 6 bits for example as in FIG. 5 b instead of the4 shown in FIG. 9). Alternatively, rather than group all of thenon-anchor carriers together, desired aggregation levels may be signaledseparately for each of the distinct bands that the UA's carriers belongto because, for example, the path loss for carriers at differentfrequencies may be different. Also, instead of binary flags thatindicate which specific aggregation levels are enabled or disabled, atwo-bit field may be used to signal the target aggregation level foreach distinct carrier or band for example using a message as in FIGS. 5c, 5 d, and 5 e.

In various implementations, UA 10 may be programmed to search only atthe target aggregation level (for either the anchor and/or non-anchorcarriers) for example using a message as in FIG. 5 c. In otherimplementations UA 10 may be programmed to search beginning with aspecified aggregation level and continuing with any higher aggregationlevels as shown in FIG. 10 for example using a message as in FIG. 5 d.In still other embodiments UA 10 may be programmed to search at a targetaggregation level and in the immediately adjacent aggregation levels asshown in FIG. 11 for example using a message as in FIG. 5 e.

To minimize the likelihood that contact with a particular UA 10 is lost,access device 12 may be configured to ensure that successivetransmissions of the MAC control element have at least one enabledaggregation level in common with one another, and that this commonaggregation level(s) will be used until access device 12 becomesreasonably certain (e.g., passes a pre-defined certain threshold) thatUA 10 has successfully received the MAC control element (e.g., nofurther HARQ retransmissions of the MAC PDU containing that MAC controlelement are required).

For example, a UA 10 may be instructed to monitor aggregation levels 1,2, and 4. If the UA's transmission channel then degrades, access device12 may wish to use higher aggregation levels when communicating with UA10. To this end, access device 12 reconfigures UA 10 to use aggregationlevels 4 and 8 (because communication at aggregation level 1 may beprone to error or other difficulties). In that case, access device 12temporarily uses only aggregation level 4 for all PDCCH transmissionsallowing UA 10 to decode those PDCCH transmissions regardless of whetherthe old or new aggregation level configuration was in use (and ensuringUA 10 receives instructions regarding the change in active aggregationlevels). In the example, access device 12 may continue using aggregationlevel 4 for a pre-defined period of time until access device 12determines, with a sufficient level of certainty, that UA 10 has appliedthe new aggregation level configuration. In that case, the contents ofthe MAC control element may be configured to be applied at a fixed time(e.g., four sub-frames) after the control element has been successfullyreceived at UA 10.

Solution 5

In some embodiments the number of aggregation levels that a UA 10searches on the PDCCH is at least partially determined by the downlinkchannel quality information (CQI) values detected by UA 10. Generally, alow CQI value corresponds to poor transmission channel conditions. Inpoor transmission channel conditions, access device 12 may be configuredto use a large aggregation level on the PDCCH for more robustcommunication with UA 10. Similarly, a high CQI value corresponds togood transmission channels, and, in that case, access device 12 may beconfigured to use a small aggregation level on the PDCCH for moreefficient communication with UA 10. As such, UA 10 may track the CQIvalues that have recently been reported to access device 12 and use theCQI information to determine which aggregation levels should be searchedon the PDCCH based upon a pre-determined algorithm.

In one example, CQI values are mapped to corresponding aggregationlevels. FIG. 13 is a table showing an example mapping of CQI values tocorresponding aggregation levels. CQI values of 1 to 3 (indicating alow-quality communication channel) map to aggregation level 8. CQIvalues of 4 to 6 map to an aggregation level of 4 and CQI values of 7-9map to an aggregation level of 2. CQI values of 10 to 15 (indicating ahigh-quality communication channel) map to an aggregation level of 1.The mapping shown in FIG. 13 is exemplary and may be adjusted based uponvarious system requirements.

To provide additional flexibility to the operation of access device 12,UA 10 may also monitor aggregation levels immediately adjacent to thetarget aggregation levels. FIG. 11 is a table showing exemplary targetaggregation levels of FIG. 13, with a listing of the resultingaggregation levels that are monitored by UA 10. A target aggregationlevel of 1 results in levels 1 and 2 being monitored. A targetaggregation level of 2 results in levels 1, 2 and 4 being monitored. Atarget aggregation level of 4 results in levels 2, 4 and 8 beingmonitored. A target aggregation level of 8 results in levels 4 and 8being monitored. In addition, whenever UA 10 changes its targetaggregation level, it may monitor the aggregation levels associated withboth the old and new target aggregation levels for a certain period oftime in order to allow access device 12 sufficient time to adjust.

Solution 6

In yet other embodiments UA 10 searches the anchor carrier over allaggregation levels. Upon detection of a valid PDCCH (i.e., a valid DCImessage), UA 10 searches the remaining carriers using the aggregationlevel associated with the valid DCI message received on the anchorcarrier and one or more other aggregation levels based on a rule setthat is either pre-defined or configured using higher layer signaling.For example, UA 10 may search the remaining carriers using theaggregation level associated with the valid DCI message on the anchorcarrier and the next most robust aggregation level. FIG. 12 is a tableshowing the detected aggregation level of an anchor carrier and theresulting aggregation levels to search on non-anchor carriers consistentwith this example. If a valid PDCCH candidate is detected on aggregationlevel 1 of the anchor carrier, levels 1 and 2 are monitored on the otheractive carriers. If a valid PDCCH candidate is detected on aggregationlevel 2 of the anchor carrier, levels 2 and 4 are monitored on the otheractive carriers. If a valid PDCCH candidate is detected on aggregationlevel 4 of the anchor carrier, levels 4 and 8 are monitored on the otheractive carriers. If a valid PDCCH candidate is detected on aggregationlevel 8 of the anchor carrier, level 8 is monitored on the other activecarriers.

In the example illustrated in FIG. 12, if UA 10 is unable to find agrant on the anchor carrier, UA 10 may be configured to search apre-defined aggregation level on each of the non-anchor carriers. Thisapproach may be implemented when the other component carriers arelocated in the same band as the anchor carrier. Otherwise, the path lossdifference between carriers may be significant and the aggregation levelon the anchor carrier may not imply the same or close aggregation levelon the other carriers.

In other implementations, it may be desirable for UA 10 to search thesearch space intelligently to reduce blind decoding and thereforeincrease battery life. Any such search algorithms, while not impactingthe capability of UA 10 to decode the entire search space as defined bythe standard, may affect the performance of the UA. For example, upondetection of a PDCCH candidate on the anchor carrier, UA 10 may searcheach of the non-anchor carriers using the aggregation level found on theanchor carrier, and then search other aggregation levels on thenon-anchor carriers. Other intelligent searching algorithms arecontemplated.

Solution 7

In still other embodiments, if UA 10 detects one of the more robustaggregation levels on an anchor carrier (e.g. 4 or 8), UA 10 may beconfigured to forego decoding the PDCCH on the non-anchor carriers.Here, it has been recognized that a robust aggregation level typicallymeans that UA 10 does not have a good channel condition. For example, UA10 may be located in the cell edge or moving very fast, thereby makingmulti-carrier operation less attractive. Such a decoding scheme can beconfigured per UA 10 or defined in a standard for normal operation. Thethreshold for the robust aggregation level may be signaled by accessdevice 12 or may be predefined.

Solution 8

In still other embodiments a new DCI message is transmitted by accessdevice 12 to indicate the aggregation levels on the non-anchor carriersto be decoded by UA 10. The message may use any of the messagestructures of FIG. 5 for each carrier or for each non-anchor carrier.For example, if UA 10 has four non-anchor carriers, then a new 16 bitDCI message (one instance of FIG. 5 a for each non-anchor carrier) maybe used based on the message structure of FIG. 5 a to indicate theaggregation levels to be searched on the non-anchor carriers.

This system implementation may be used when UA 10 may have multipleassignments in the UA-specific search space. If access device 12 isconfigured such that UA 10 can only have one assignment in theUA-specific search space, a 4-bit message may be used to indicate theexact PDCCH candidate that UA 10 should decode. Similarly, a 2-bitmessage could be used to indicate the aggregation level UA 10 shoulddecode.

The new DCI message may only be needed when access device 12 is making amulti-carrier allocation. If there is only traffic on the anchor carrierfor a particular UA 10, then the new DCI message may not be needed.Finally, if UA 10 did not detect the new DCI message from theUA-specific search space of the anchor carrier, UA 10 may not search thePDCCHs from the UA-specific search space of the remaining carriers ormay search a more limited subset of the normal PDCCH search space of theremaining carriers.

Similarly, a new field may be added to one or more existing DCI formatsto indicate the specific aggregation levels on the next carriers to bedecoded by UA 10. For instance, a DCI message on an anchor carrier mayindicate that only aggregation levels 2 and 4 should be searched for anext active carrier and a DCI message on the next active carrier mayindicate that only aggregation level 8 should be searched on thefollowing carrier and so on. The encoding of the new field may be inaccordance with the 2-bit, 4-bit, and 6-bit implementations as discussedabove.

Solution 9

In some embodiments, in the common search space, UA 10 does not need todecode the PDCCH on all carriers for some RNTIs. For example, the systeminformation RNTI (SI-RNTI), paging RNTI (P-RNTI), and random access RNTI(RA-RNTI) may only be blind decoded on the anchor carrier. Because UA 10may be configured to not decode DCI format 1C in the non-anchorcarriers, it is contemplated that such a system implementation wouldreduce the number of blind decodes.

Solution 10

In still other implementations the DCI candidates on a carrier K arerestricted by successfully decoded DCI formats on carrier K−1. Forexample, if a UA 10 is configured to search for DCI format 2 and the UA10 detects DCI format 2 on its anchor carrier, then UA 10 may beprogrammed to only perform blind decoding using DCI format 2 on theremaining active carriers. This may only be possible for certain DCIformats.

Solution 11

If power control is defined per carrier, higher layer signaling may beused to configure multiple transmission power control (TPC) indices thatcorrespond to multiple carriers using a single control message for asingle UA 10. Access device 12 may signal a TPC-index per carrierconfigured to a given UA 10. Alternatively, access device 12 may signala TPC-Index of an anchor carrier, with each UA 10 calculating aTPC-index. In one implementation, UA 10 uses an equation, such asTPC-index of carrier c=TPC-index of anchor carrier+(c−c_a), where c_a isthe carrier index of the anchor carrier. In one implementation, UA 10only monitors DCI format 3/3A on a single component carrier, while beingable to receive power control commands for multiple carriers.

Solution 12

In still other embodiments where a UA 10 is assigned a set of activecarriers and one of the active carriers is assigned as an anchorcarrier, UA 10 performs blind decoding using a decoding process (e.g.,as described by the LTE Rel-8) or a slightly reduced blind decodingprocess on the anchor carrier as described above. UA 10 also performsblind decoding on any remaining active carriers (non-anchor carriers)using a reduced search space. The reduced search space may beestablished in any one of the ways described above. In oneimplementation, the step of decoding on the remaining active carriers isonly performed if UA 10 successfully decodes one or more PDCCHcandidates on the anchor carrier. If there is no traffic on the anchorcarrier and there is traffic on one or more of the non-anchor carriers,one or more of the network components, such as an eNB or other accessdevice 12 may use a dummy transmission on the PDCCH to trigger decodingon the non-anchor carriers. In other implementations, UA 10 decodes onany remaining active carriers whether or not UA 10 successfully decodesone or more PDCCH candidates on the anchor carrier.

In the present system, the reduced search space may be defined as asubset of the CCE subset candidates based on the RNTI of the UA 10.Alternatively, the search space may be defined using a linearcongruential random number generator as described in LTE standards (Seesection 9 of 3GPP TS 36.213). In the present system, random numbergeneration may be implemented using two different algorithms. First, therecursion may apply in the component carrier domain instead of the timedomain. Second, the recursion may apply in the time domain as in LTERel-8. The initial value, however, may be a function of the RNTI and acomponent carrier index.

The control region consists of a set of CCEs, numbered from 0 toN_(CCE,k,c)−1 according to Section 6.8.2 in 3GPP TS 36.211, whereN_(CCE,k,c) is the total number of CCEs in the control region ofsub-frame k of component carrier c. UA 10 shall monitor a set of PDCCHcandidates for control information in every non-DRX sub-frame, wheremonitoring implies attempting to decode each of the PDCCHs in the setaccording to all the monitored DCI formats.

The set of PDCCH candidates to monitor are defined in terms of searchspaces, where a search space S_(k) ^((L)) at aggregation levelLε{1,2,4,8} is defined by a set of PDCCH candidates. The CCEs forcomponent carrier c corresponding to PDCCH candidate m of the searchspace S_(k,c) ^((L)) are given byL{(Y _(k,c) +m)mod └N _(CCE,k) /L┘}+iwhere Y_(k,c) is defined below, i=0, . . . , L−1 and m=0, . . . ,M^((L,c))−1. M^((L,c)) is the number of PDCCH candidates to monitor inthe given search space.

For the anchor carrier, UA 10 shall monitor each of the candidates m=0,. . . , M^((L,c))−1. For the remaining carriers, UA 10 shall monitoraggregation levels and/or candidates as configured by RRC or asindicated by the PDCCH or as indicated by a MAC control element.

The UA 10 shall monitor one common search space at each of theaggregation levels 4 and 8 and one UA-specific search space at each ofthe aggregation levels 1, 2, 4, 8. The common and UA-specific searchspaces may overlap.

The aggregation levels defining the search spaces are listed in tableshown in FIG. 15. The DCI formats that UA 10 shall monitor depend on theconfigured transmission mode as defined in Section 7.1 in 3GPP TS36.213.

Option 1

For the common search spaces, Y_(k,c) is set to 0 for the twoaggregation levels 4 and 8.

For the UA-specific search space S_(k,c) ^((L)) at aggregation level L,the variable Y_(k,c) defined byY _(k,c)=(A·Y _(k-1,c))mod D c=0Y _(k,c)=(A·Y _(k,c-1))mod D c>0OrY _(k,c)=(A·Y _(k-1,c))mod D c=c _(a)Y _(k,c)=(A·Y _(k,c-1))mod D c≠c _(a)

where Y_(−1,0)=n_(RNTI)≠0, A=39827, D=65537 and k=└n_(s)/2┘, n_(s) isthe slot number within a radio frame. The RNTI value used for n_(RNTI)is defined in section 7.1 in downlink and section 8 in uplink in 3GPP TS36.213.

Option 2

For the common search spaces, Y_(k,c) is set to 0 for the twoaggregation levels 4 and 8.

For the UA-specific search space S_(k,c) ^((L)) at aggregation level L,the variable Y_(k,c) is defined byY _(k,c)=(A·Y _(k-1,c))mod Dwhere Y_(−1,c)=f(n_(RNTI),c)mod D≠0, A=39827, D=65337 and k=└n_(s)/2┘,n_(s) is the slot number within a radio frame. The RNTI value used forn_(RNTI) is defined in section 7.1 in downlink and section 8 in uplinkin 3GPP TS 36.213.

In some embodiments, f(n_(RNTI),c)=n_(RNTI)+c.

In other embodiments, f(n_(RNTI),c)=n_(RNTI)·c.

The above steps generate a search in both common and UA-specific spacesas depicted in FIG. 14 where clear space is searched and cross hatchedspace is not searched. The location of the UA-specific search spaces 88,90, and 92 are random from carrier to carrier providing benefits forinterference averaging. In contrast, the common search space 94 may bethe same for all component carriers. In one implementation, UA-specificsearch space 88 in the anchor carrier may be as defined in LTE Rel-8.The UA-specific search spaces 90 and 92 in the remaining active carriersmay be as small as one PDCCH candidate per aggregation level.

Solution 13

Another solution to reduce the number of blind decodings is toprioritize the blind decoding within the search space. Multiple searchspaces can be defined for a UA. These search spaces may not beassociated with a particular carrier. LTE Rel-8 defines one search spacefor a UA-specific messages as well as a common search space, which canbe used for UA specific messages and broadcast messages. FIG. 20 showsan example of multiple search spaces. In the illustrated example, eachof three separate UAs UA1, UA2 and UA3 is assigned two search spaces,denoted primary and secondary search spaces.

Different set of PDCCH candidates for each search space can be definedor same PDCCH candidates can be used. In other words, the aggregationlevels and the number of PDCCH candidates used in the primary andsecondary search space can be different. The same PDCCH candidatesresults in the same search space size. The locations of multiple searchspaces may consist of different CCEs but the search spaces may alsooverlap each other. If multiple search spaces are located consecutively(i.e., the primary search space is defined by LTE Rel-8 method and thesecondary search space is located right after the primary search space)or based on a fixed rule (e.g. the primary search space is defined bythe LTE Rel-8 method and the secondary search space is located a fixeddistance from the primary search space), an additional parameter todefine the secondary search space should not be required. Otherwise, anadditional parameter may be necessary to define multiple search spaces.This additional parameter to define the secondary search space can besignaled by higher layer signaling or fixed in a communication protocolspecification. In some embodiments, only the primary search spaceincludes a common search space. In some embodiments, the equationsdescribed above to determine the location of a search space for multiplecomponent carriers based on a component carrier index c are modified sothat they are based on a search space index, denoted ssi, simply byreplacing c with ssi in the equations above.

The UA monitors the multiple search spaces at every subframe. In oneembodiment, the primary search space is monitored first by the UA andthe secondary search space is monitored if the UA cannot detect any DCIformat with the same category in the primary search space. DCI formatshaving a similar purpose can be included in the same category. Forexample, DL DCI format configured with C-RNTI and DL DCI formatconfigured with SPS-RNTI are used to schedule downlink resources, sothey can be considered to be part of the same category. However, UL DCIformat configured with C-RNTI is for allocating uplink resources so itwould not be included in a same category as DL DCI format. In otherembodiments, the primary search space is monitored first by the UA andthe secondary search space is only monitored under certain conditions.For example, in some embodiments, the secondary search space is onlymonitored if the primary search space includes an instruction to monitorthe secondary search space. In other embodiments, the secondary searchspace is not monitored if the UE detects any valid DCI format in theprimary search space.

The eNB will be able to transmit PDCCH in the primary search space firstif the primary search space is not overloaded and the UA will, in thatcase, only have to monitor the primary search space and this techniquewill reduce the number of blind decoding attempts by the UA.

In other embodiments, the primary search space is used to control theamount or type of blind decoding performed in the secondary searchspace. The above solutions can be applied to multiple search spaces onthe same carrier. For example, in solution 5, the UA searches the anchorcarrier for all aggregation levels. Upon detection of a valid PDCCH, theUA searches the remaining carriers using the aggregation level found onthe anchor carrier and one or more other aggregation levels based on arule as defined in the standard or defined using higher layer signaling.Extending this to multiple search spaces on the same carrier, the UA maysearch the primary search space for all aggregation levels. Upondetection of a valid PDCCH, the UA may search the secondary search spaceusing the aggregation level found on the primary search space and one ormore other aggregation levels based on a rule as defined in the standardor defined using higher layer signaling.

The size of the secondary search space can depend on the number ofcarriers configured at the UA. In some embodiments, the primary searchspace is used for carriers corresponding to a first transmission modeand the secondary search space is used for carriers corresponding to asecond transmission mode. In some embodiments, the primary search spaceis used for carriers corresponding to a first bandwidth and thesecondary search space is used for carriers corresponding to a secondbandwidth. In some embodiments, the primary search space is used for oneor more designated carriers (e.g. anchor carrier), and the secondarysearch space is used for one or more non-designated carriers (e.g.non-anchor carriers).

FIG. 16 illustrates a wireless communications system including anembodiment of UA 10. UA 10 is operable for implementing aspects of thedisclosure, but the disclosure should not be limited to theseimplementations. Though illustrated as a mobile phone, the UA 10 maytake various forms including a wireless handset, a pager, a personaldigital assistant (PDA), a portable computer, a tablet computer, alaptop computer. Many suitable devices combine some or all of thesefunctions. In some embodiments of the disclosure, the UA 10 is not ageneral purpose computing device like a portable, laptop or tabletcomputer, but rather is a special-purpose communications device such asa mobile phone, a wireless handset, a pager, a PDA, or atelecommunications device installed in a vehicle. The UA 10 may also bea device, include a device, or be included in a device that has similarcapabilities but that is not transportable, such as a desktop computer,a set-top box, or a network node. The UA 10 may support specializedactivities such as gaming, inventory control, job control, and/or taskmanagement functions, and so on.

The UA 10 includes a display 702. The UA 10 also includes atouch-sensitive surface, a keyboard or other input keys generallyreferred as 704 for input by a user. The keyboard may be a full orreduced alphanumeric keyboard such as QWERTY, Dvorak, AZERTY, andsequential types, or a traditional numeric keypad with alphabet lettersassociated with a telephone keypad. The input keys may include atrackwheel, an exit or escape key, a trackball, and other navigationalor functional keys, which may be inwardly depressed to provide furtherinput function. The UA 10 may present options for the user to select,controls for the user to actuate, and/or cursors or other indicators forthe user to direct.

The UA 10 may further accept data entry from the user, including numbersto dial or various parameter values for configuring the operation of theUA 10. The UA 10 may further execute one or more software or firmwareapplications in response to user commands. These applications mayconfigure the UA 10 to perform various customized functions in responseto user interaction. Additionally, the UA 10 may be programmed and/orconfigured over-the-air, for example from a wireless base station, awireless access point, or a peer UA 10.

Among the various applications executable by the UA 10 are a webbrowser, which enables the display 702 to show a web page. The web pagemay be obtained via wireless communications with a wireless networkaccess node, a cell tower, a peer UA 10, or any other wirelesscommunication network or system 700. The network 700 is coupled to awired network 708, such as the Internet. Via the wireless link and thewired network, the UA 10 has access to information on various servers,such as a server 710. The server 710 may provide content that may beshown on the display 702. Alternately, the UA 10 may access the network700 through a peer UA 10 acting as an intermediary, in a relay type orhop type of connection.

FIG. 17 shows a block diagram of the UA 10. While a variety of knowncomponents of UAs 110 are depicted, in an embodiment a subset of thelisted components and/or additional components not listed may beincluded in the UA 10. The UA 10 includes a digital signal processor(DSP) 802 and a memory 804. As shown, the UA 10 may further include anantenna and front end unit 806, a radio frequency (RF) transceiver 808,an analog baseband processing unit 810, a microphone 812, an earpiecespeaker 814, a headset port 816, an input/output interface 818, aremovable memory card 820, a universal serial bus (USB) port 822, ashort range wireless communication sub-system 824, an alert 826, akeypad 828, a liquid crystal display (LCD), which may include a touchsensitive surface 830, an LCD controller 832, a charge-coupled device(CCD) camera 834, a camera controller 836, and a global positioningsystem (GPS) sensor 838. In an embodiment, the UA 10 may include anotherkind of display that does not provide a touch sensitive screen. In anembodiment, the DSP 802 may communicate directly with the memory 804without passing through the input/output interface 818.

The DSP 802 or some other form of controller or central processing unitoperates to control the various components of the UA 10 in accordancewith embedded software or firmware stored in memory 804 or stored inmemory contained within the DSP 802 itself. In addition to the embeddedsoftware or firmware, the DSP 802 may execute other applications storedin the memory 804 or made available via information carrier media suchas portable data storage media like the removable memory card 820 or viawired or wireless network communications. The application software maycomprise a compiled set of machine-readable instructions that configurethe DSP 802 to provide the desired functionality, or the applicationsoftware may be high-level software instructions to be processed by aninterpreter or compiler to indirectly configure the DSP 802.

The antenna and front end unit 806 may be provided to convert betweenwireless signals and electrical signals, enabling the UA 10 to send andreceive information from a cellular network or some other availablewireless communications network or from a peer UA 10. In an embodiment,the antenna and front end unit 806 may include multiple antennas tosupport beam forming and/or multiple input multiple output (MIMO)operations. As is known to those skilled in the art, MIMO operations mayprovide spatial diversity which can be used to overcome difficultchannel conditions and/or increase channel throughput. The antenna andfront end unit 806 may include antenna tuning and/or impedance matchingcomponents, RF power amplifiers, and/or low noise amplifiers.

The RF transceiver 808 provides frequency shifting, converting receivedRF signals to baseband and converting baseband transmit signals to RF.In some descriptions a radio transceiver or RF transceiver may beunderstood to include other signal processing functionality such asmodulation/demodulation, coding/decoding, interleaving/deinterleaving,spreading/despreading, inverse fast Fourier transforming (IFFT)/fastFourier transforming (FFT), cyclic prefix appending/removal, and othersignal processing functions. For the purposes of clarity, thedescription here separates the description of this signal processingfrom the RF and/or radio stage and conceptually allocates that signalprocessing to the analog baseband processing unit 810 and/or the DSP 802or other central processing unit. In some embodiments, the RFTransceiver 808, portions of the Antenna and Front End 806, and theanalog baseband processing unit 810 may be combined in one or moreprocessing units and/or application specific integrated circuits(ASICs).

The analog baseband processing unit 810 may provide various analogprocessing of inputs and outputs, for example analog processing ofinputs from the microphone 812 and the headset 816 and outputs to theearpiece 814 and the headset 816. To that end, the analog basebandprocessing unit 810 may have ports for connecting to the built-inmicrophone 812 and the earpiece speaker 814 that enable the UA 10 to beused as a cell phone. The analog baseband processing unit 810 mayfurther include a port for connecting to a headset or other hands-freemicrophone and speaker configuration. The analog baseband processingunit 810 may provide digital-to-analog conversion in one signaldirection and analog-to-digital conversion in the opposing signaldirection. In some embodiments, at least some of the functionality ofthe analog baseband processing unit 810 may be provided by digitalprocessing components, for example by the DSP 802 or by other centralprocessing units.

The DSP 802 may perform modulation/demodulation, coding/decoding,interleaving/deinterleaving, spreading/despreading, inverse fast Fouriertransforming (IFFT)/fast Fourier transforming (FFT), cyclic prefixappending/removal, and other signal processing functions associated withwireless communications. In an embodiment, for example in a codedivision multiple access (CDMA) technology application, for atransmitter function the DSP 802 may perform modulation, coding,interleaving, and spreading, and for a receiver function the DSP 802 mayperform despreading, deinterleaving, decoding, and demodulation. Inanother embodiment, for example in an orthogonal frequency divisionmultiplex access (OFDMA) technology application, for the transmitterfunction the DSP 802 may perform modulation, coding, interleaving,inverse fast Fourier transforming, and cyclic prefix appending, and fora receiver function the DSP 802 may perform cyclic prefix removal, fastFourier transforming, deinterleaving, decoding, and demodulation. Inother wireless technology applications, yet other signal processingfunctions and combinations of signal processing functions may beperformed by the DSP 802.

The DSP 802 may communicate with a wireless network via the analogbaseband processing unit 810. In some embodiments, the communication mayprovide Internet connectivity, enabling a user to gain access to contenton the Internet and to send and receive e-mail or text messages. Theinput/output interface 818 interconnects the DSP 802 and variousmemories and interfaces. The memory 804 and the removable memory card820 may provide software and data to configure the operation of the DSP802. Among the interfaces may be the USB interface 822 and the shortrange wireless communication sub-system 824. The USB interface 822 maybe used to charge the UA 10 and may also enable the UA 10 to function asa peripheral device to exchange information with a personal computer orother computer system. The short range wireless communication sub-system824 may include an infrared port, a Bluetooth interface, an IEEE 802.11compliant wireless interface, or any other short range wirelesscommunication sub-system, which may enable the UA 10 to communicatewirelessly with other nearby mobile devices and/or wireless basestations.

The input/output interface 818 may further connect the DSP 802 to thealert 826 that, when triggered, causes the UA 10 to provide a notice tothe user, for example, by ringing, playing a melody, or vibrating. Thealert 826 may serve as a mechanism for alerting the user to any ofvarious events such as an incoming call, a new text message, and anappointment reminder by silently vibrating, or by playing a specificpre-assigned melody for a particular caller.

The keypad 828 couples to the DSP 802 via the interface 818 to provideone mechanism for the user to make selections, enter information, andotherwise provide input to the UA 10. The keyboard 828 may be a full orreduced alphanumeric keyboard such as QWERTY, Dvorak, AZERTY andsequential types, or a traditional numeric keypad with alphabet lettersassociated with a telephone keypad. The input keys may include atrackwheel, an exit or escape key, a trackball, and other navigationalor functional keys, which may be inwardly depressed to provide furtherinput function. Another input mechanism may be the LCD 830, which mayinclude touch screen capability and also display text and/or graphics tothe user. The LCD controller 832 couples the DSP 802 to the LCD 830.

The CCD camera 834, if equipped, enables the UA 10 to take digitalpictures. The DSP 802 communicates with the CCD camera 834 via thecamera controller 836. In another embodiment, a camera operatingaccording to a technology other than Charge Coupled Device cameras maybe employed. The GPS sensor 838 is coupled to the DSP 802 to decodeglobal positioning system signals, thereby enabling the UA 10 todetermine its position. Various other peripherals may also be includedto provide additional functions, e.g., radio and television reception.

FIG. 18 illustrates a software environment 902 that may be implementedby the DSP 802. The DSP 802 executes operating system drivers 904 thatprovide a platform from which the rest of the software operates. Theoperating system drivers 904 provide drivers for the UA hardware withstandardized interfaces that are accessible to application software. Theoperating system drivers 904 include application management services(“AMS”) 906 that transfer control between applications running on the UA10. Also shown in FIG. 18 are a web browser application 908, a mediaplayer application 910, and Java applets 912. The web browserapplication 908 configures the UA 10 to operate as a web browser,allowing a user to enter information into forms and select links toretrieve and view web pages. The media player application 910 configuresthe UA 10 to retrieve and play audio or audiovisual media. The Javaapplets 912 configure the UA 10 to provide games, utilities, and otherfunctionality. A component 914 might provide functionality describedherein.

The UA 10, access device 120, and other components described above mightinclude a processing component that is capable of executing instructionsrelated to the actions described above. FIG. 19 illustrates an exampleof a system 1000 that includes a processing component 1010 suitable forimplementing one or more embodiments disclosed herein. In addition tothe processor 1010 (which may be referred to as a central processor unit(CPU or DSP), the system 1000 might include network connectivity devices1020, random access memory (RAM) 1030, read only memory (ROM) 1040,secondary storage 1050, and input/output (I/O) devices 1060. In someembodiments, a program for implementing the determination of a minimumnumber of HARQ process IDs may be stored in ROM 1040. In some cases,some of these components may not be present or may be combined invarious combinations with one another or with other components notshown. These components might be located in a single physical entity orin more than one physical entity. Any actions described herein as beingtaken by the processor 1010 might be taken by the processor 1010 aloneor by the processor 1010 in conjunction with one or more componentsshown or not shown in the drawing.

The processor 1010 executes instructions, codes, computer programs, orscripts that it might access from the network connectivity devices 1020,RAM 1030, ROM 1040, or secondary storage 1050 (which might includevarious disk-based systems such as hard disk, floppy disk, or opticaldisk). While only one processor 1010 is shown, multiple processors maybe present. Thus, while instructions may be discussed as being executedby a processor, the instructions may be executed simultaneously,serially, or otherwise by one or multiple processors. The processor 1010may be implemented as one or more CPU chips.

The network connectivity devices 1020 may take the form of modems, modembanks, Ethernet devices, universal serial bus (USB) interface devices,serial interfaces, token ring devices, fiber distributed data interface(FDDI) devices, wireless local area network (WLAN) devices, radiotransceiver devices such as code division multiple access (CDMA)devices, global system for mobile communications (GSM) radio transceiverdevices, worldwide interoperability for microwave access (WiMAX)devices, and/or other well-known devices for connecting to networks.These network connectivity devices 1020 may enable the processor 1010 tocommunicate with the Internet or one or more telecommunications networksor other networks from which the processor 1010 might receiveinformation or to which the processor 1010 might output information.

The network connectivity devices 1020 might also include one or moretransceiver components 1025 capable of transmitting and/or receivingdata wirelessly in the form of electromagnetic waves, such as radiofrequency signals or microwave frequency signals. Alternatively, thedata may propagate in or on the surface of electrical conductors, incoaxial cables, in waveguides, in optical media such as optical fiber,or in other media. The transceiver component 1025 might include separatereceiving and transmitting units or a single transceiver. Informationtransmitted or received by the transceiver 1025 may include data thathas been processed by the processor 1010 or instructions that are to beexecuted by processor 1010. Such information may be received from andoutputted to a network in the form, for example, of a computer databaseband signal or signal embodied in a carrier wave. The data may beordered according to different sequences as may be desirable for eitherprocessing or generating the data or transmitting or receiving the data.The baseband signal, the signal embedded in the carrier wave, or othertypes of signals currently used or hereafter developed may be referredto as the transmission medium and may be generated according to severalmethods well known to one skilled in the art.

The RAM 1030 might be used to store volatile data and perhaps to storeinstructions that are executed by the processor 1010. The ROM 1040 is anon-volatile memory device that typically has a smaller memory capacitythan the memory capacity of the secondary storage 1050. ROM 1040 mightbe used to store instructions and perhaps data that are read duringexecution of the instructions. Access to both RAM 1030 and ROM 1040 istypically faster than to secondary storage 1050. The secondary storage1050 is typically comprised of one or more disk drives or tape drivesand might be used for non-volatile storage of data or as an over-flowdata storage device if RAM 1030 is not large enough to hold all workingdata. Secondary storage 1050 may be used to store programs that areloaded into RAM 1030 when such programs are selected for execution.

The I/O devices 1060 may include liquid crystal displays (LCDs), touchscreen displays, keyboards, keypads, switches, dials, mice, track balls,voice recognizers, card readers, paper tape readers, printers, videomonitors, or other well-known input/output devices. Also, thetransceiver 1025 might be considered to be a component of the I/Odevices 1060 instead of or in addition to being a component of thenetwork connectivity devices 1020. Some or all of the I/O devices 1060may be substantially similar to various components depicted in thepreviously described drawing of the UA 10, such as the display 702 andthe input 704.

The following 3rd Generation Partnership Project (3GPP) TechnicalSpecifications (TS) are incorporated herein by reference: TS 36.321, TS36.331, and TS 36.300, TS 36.211, TS 36.212 and TS 36.213.

While several embodiments have been provided in the present disclosure,it should be understood that the disclosed systems and methods may beembodied in many other specific forms without departing from the spiritor scope of the present disclosure. The present examples are to beconsidered as illustrative and not restrictive, and the intention is notto be limited to the details given herein. For example, the variouselements or components may be combined or integrated in another systemor certain features may be omitted, or not implemented.

Also, techniques, systems, subsystems and methods described andillustrated in the various embodiments as discrete or separate may becombined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as coupled or directly coupled orcommunicating with each other may be indirectly coupled or communicatingthrough some interface, device, or intermediate component, whetherelectrically, mechanically, or otherwise. Other examples of changes,substitutions, and alterations are ascertainable by one skilled in theart and could be made without departing from the spirit and scopedisclosed herein.

To apprise the public of the scope of this invention, the followingclaims are made:

What is claimed is:
 1. A method performed by a user equipment ‘UE’ thatis configured to perform Long Term Evolution ‘LTE’ carrier aggregationoperations, the method comprising: identifying one carrier as an anchorcarrier and at least one other carrier as a non-anchor carrier; decodinga physical downlink control channel (PDCCH) in a common search space ofonly the anchor carrier; and decoding the PDCCH in a UE specific searchspace of the anchor carrier; and decoding a PDCCH in a UE specificsearch space of the at least one non-anchor carrier; wherein thelocation of the UE specific search space of the anchor carrier variespseudo-randomly for different sub-frames.
 2. The method of claim 1,wherein the common search space of the anchor carrier and UE specificsearch space of the anchor carrier overlap.
 3. The method of claim 1,wherein decoding a PDCCH in a common search space comprises decodingPDCCH using a random access radio network terminal identifier (RNTI). 4.The method of claim 1, further comprising receiving via radio resourcecontrol (RRC) signaling an indication that at least one aggregationlevel corresponding to the common search space is not used.
 5. Themethod of claim 1, further comprising: receiving a first indicationcorresponding to a power control index for the anchor carrier; receivinga second indication corresponding to a power control index for the atleast one non-anchor carrier; and determining power control commands forthe anchor carrier at the at least one non-anchor carrier based on thereceived indications and PDCCH decoded in the common search space. 6.The method of claim 5, wherein the PDCCH is at least one of downlinkcontrol information format 3 or downlink control information format 3A.7. The method of claim 1, wherein the anchor carrier and the at leastone non-anchor carrier are identified based on radio resource controlsignaling.
 8. The method of claim 1, wherein the PDCCH in the UEspecific search space of the anchor carrier is the same as the PDCCH inthe UE specific search space of the at least one non-anchor carrier. 9.A user equipment (“UE”) comprising: a processor configured to: identifyone carrier as an anchor carrier and at least one other carrier as anon-anchor carrier; decode a physical downlink control channel (PDCCH)in a common search space of only the anchor carrier; and decoding thePDCCH in a UE specific search space of the anchor carrier; and decodinga PDCCH in a UE specific search space of the at least one non-anchorcarrier; wherein the location of the UE specific search space of theanchor carrier varies pseudo-randomly for different sub-frames.
 10. TheUE of claim 9, wherein the common search space of the anchor carrier andUE specific search space of the anchor carrier overlap.
 11. The UE ofclaim 9, wherein decoding a PDCCH in a common search space comprisesdecoding PDCCH using a random access radio network terminal identifier(RNTI).
 12. The UE of claim 9, the processor further configured toreceive via radio resource control (RRC) signaling an indication that atleast one aggregation level corresponding to the common search space isnot used.
 13. The UE of claim 9, the processor further configured to:receive a first indication corresponding to a power control index forthe anchor carrier; receive a second indication corresponding to a powercontrol index for the at least one non-anchor carrier; and determinepower control commands for the anchor carrier at the at least onenon-anchor carrier based on the received indications and PDCCH decodedin the common search space.
 14. The UE of claim 13, wherein the PDCCH isat least one of downlink control information format 3 or downlinkcontrol information format 3A.
 15. The UE of claim 9, wherein the anchorcarrier and the at least one non-anchor carrier are identified based onradio resource control signaling.
 16. The UE of claim 9, wherein thePDCCH in the UE specific search space of the anchor carrier is the sameas the PDCCH in the UE specific search space of the at least onenon-anchor carrier.
 17. A tangible computer program product storingcomputer readable instructions configured to cause a processor of a userequipment ‘UE’ to: identify one carrier as an anchor carrier and atleast one other carrier as a non-anchor carrier; only decode PDCCH in acommon search space of an anchor carrier to reduce a number of blinddecodes; and decoding the PDCCH in a UE specific search space of theanchor carrier; and decoding a PDCCH in a UE specific search space ofthe at least one non-anchor carrier, wherein the location of the UEspecific search space of the anchor carrier varies pseudo-randomly fordifferent sub-frames.
 18. The computer program product of claim 17,wherein the common search space of the anchor carrier and UE specificsearch space of the anchor carrier overlap.
 19. The computer programproduct of claim 17, wherein decoding a PDCCH in a common search spacecomprises decoding PDCCH using a random access radio network terminalidentifier (RNTI).
 20. The computer program product of claim 17, whereininstructions cause the processor to receive via radio resource control(RRC) signaling an indication that at least one aggregation levelcorresponding to the common search space is not used.
 21. The computerprogram product of claim 17, wherein instructions cause the processorto: receive a first indication corresponding to a power control indexfor the anchor carrier; receive a second indication corresponding to apower control index for the at least one non-anchor carrier; anddetermine power control commands for the anchor carrier at the at leastone non-anchor carrier based on the received indications and PDCCHdecoded in the common search space.
 22. The computer program product ofclaim 21, wherein the PDCCH is at least one of downlink controlinformation format 3 or downlink control information format 3A.
 23. Thecomputer program product of claim 17, wherein the anchor carrier and theat least one non-anchor carrier are identified based on radio resourcecontrol signaling.
 24. The computer program product of claim 17, whereinthe PDCCH in the UE specific search space of the anchor carrier is thesame as the PDCCH in the UE specific search space of the at least onenon-anchor carrier.